Depolarization Ratio of the ν1 Raman Band of Pure CH4 and Perturbed by N2 and CO2

In this work, the effect of nitrogen and carbon dioxide on the depolarization ratio of the ν1 band of methane in the pressure range of 0.1–5 MPa is studied. A high-sensitivity single-pass Raman spectrometer was used to obtain accurate results. Moreover, we took into account the overlap of the ν1 band by the ν3 and ν2 + ν4 bands using the simulation of their spectra. The depolarization ratio of the ν1 band in pure methane is within 0–0.001, and the effect of nitrogen and carbon dioxide on this parameter is negligible in the indicated pressure range. The obtained results are useful for correct simulation of the Raman spectrum of methane at different pressures, which is necessary to improve the accuracy of gas analysis methods using Raman spectroscopy.

Crystallization of Isotactic Polypropylene Nanocomposites with Fibrillated Poly(tetrafluoroethylene) under Elevated Pressure

Nanocomposites of isotactic polypropylene with 1–5 wt.% of fibrillated PTFE (PP/T) were prepared, and their crystallization during cooling under elevated pressure, in a wide pressure range, up to 300 MPa, as well as the resulting structure, were examined. The crystallization peak temperatures of PP/T, especially with 3 and 5 wt.% of PTFE, exceeded by up to 13 °C those of neat PP. Moreover, a fine-grain structure was formed in PP/T in the entire pressure range, which proved the ability of the fibrillated PTFE to nucleate crystallization of PP in the γ-form under elevated pressure. This also resulted in a higher crystallinity level developed in the γ-domain, before the temperature range of the α-domain was reached during cooling. Hence, the γ-content increased in comparison to that in neat PP, under the pressure up to 200 MPa, especially under 50–100 MPa.

First-Order Phase Transformation at Constant Volume: A Continuous Transition?

We describe a first-order phase transition of a simple system in a process where the volume is kept constant. We show that, unlike what happens when the pressure is constant, (i) the transformation extends over a finite temperature (and pressure) range, (ii) each and every extensive potential (internal energy U, enthalpy H, Helmholtz energy F, and Gibbs energy G), and the entropy S is continuous across the transition, and (iii) the constant-volume heat capacity does not diverge during the transition and only exhibits discrete jumps. These non-intuitive results highlight the importance of controlling the correct variables in order to distinguish between continuous and discontinuous transitions. We apply our results to describe the transition between ice VI and liquid water using thermodynamic information available in the literature and also to show that a first-order phase transition driven in isochoric condition can be used as the operating principle of a mechanical actuator.

THERMODYNAMIC PROPERTIES AND THE EQUATION OF STATE OF COPPER

Высокотемпературное уравнение состояния меди получено с использованием экспериментальных данных по термодинамическим свойствам, объемному термическому расширению, сжимаемости, температурной зависимости модуля объемного сжатия. Весь объем экспериментальных данных оптимизирован с использованием температурно-зависящего уравнения Тайта в диапазоне давлений до 2000 кбар и температур от 20-50 K до температуры плавления. Температурная зависимость термодинамических и термофизических параметров описана с использованием расширенной модели Эйнштейна. Полученное уравнение состояния хорошо описывает весь объем экспериментальных данных в пределах погрешности измерений отдельных величин. The high-temperature equation of state of copper is obtained using experimental data on thermodynamic properties, volumetric thermal expansion, compressibility, temperature dependence of the volumetric compression modulus. The entire volume of experimental data is optimized using the temperature-dependent Tate equation in the pressure range up to 2000 kbar and temperatures from 20-50 K to the melting point. The temperature dependence of thermodynamic and thermophysical parameters is described using the extended Einstein model. The resulting equation of state describes well the entire volume of experimental data within the measurement error of individual quantities.

INFLUENCE OF NANODISPERSED METAL POWDERS ON THE COMBUSTION OF ENERGY CONDENSED SYSTEMS BASED ON AMMONIUM NITRATE WITH DIFFERENT TYPE OF POLYMER BINDER

Определены особенности горения энергетических композиций на основе инертного и активного горючих-связующих с нитратом аммония в диапазоне давлений до 10 Мпа. Представлен сравнительный анализ влияния наноразмерных порошков металлов на процесс горения композиций с различными наполнителями: октоген, нитрат аммония, CL-20. Показана эффективность нанопорошков металлов (Cu, Ni, Mo, Al, Zn) и неметалла (B) в качестве катализаторов горения. The features of combustion of energy compositions based on inert and active combustible binders with ammonium nitrate in the pressure range up to 10 MPa have been determined. A comparative analysis of the effect of nanosized metal powders on the combustion process of compositions with various fillers: HMX, ammonium nitrate, CL-20 is presented. The efficiency of metal (Cu, Ni, Mo, Al, Zn) and non-metal (B) nano powders as combustion catalysts is shown.

Theoretical Basis of Face Contact Pressure Design of Zero-leakage Mechanical Seal

Based on the percolation theory, the critical porosity of zero-leakage at the wetting and non-wetting sealing interface working in liquid medium is first discussed. The influence of end-face frictional heat on end-face friction and wear is then investigated. The design criteria for the face contact pressure of mechanical seals with zero-leakage and long-life operation are established. Afterwards, the face contact pressure range of the mechanical seal working in conventional different liquid medium is calculated, and the influence of different working conditions speed, medium temperature and pressure on the face contact pressure range change is analyzed. Existing studies have shown that mechanical seals can achieve zero-leakage and long-life operation. As for the wettable sealing interface, the minimum face contact pressure, corresponding to the zero-leakage condition, is only related to the morphological parameters of the sealing interface, and has nothing to do with the sealing medium. Under the rotating and stationary rings physical parameters and given working conditions, the face contact pressure range of the sealing medium water and propane propylene is 0.477~1.132 MPa. The diesel sealing medium has a larger face contact pressure range than that of water and propane propylene, which can reach 0.477~2.183 MPa. The working condition speed, medium temperature and medium pressure have an influence on the face contact pressure range, while the influence of the working condition speed is the most significant.

The Waste Recycling of Sugarcane Bagasse-Based Biochar for Biogas Purification

The utilization of the recycling of biomass waste for carbon dioxide (CO2) adsorption in biogas is still rare. Even though the experiments on the biogas purification still using synthetic biogas. This paper investigated the recycling of biomass waste, sugarcane bagasse for biogas purification. The conversion of biomass into biochar was claimed to expand the surface area of its pores for capturing CO2 in biogas. Five treatments of adsorbents used in this study, 100% volume of zeolite or biochar, 75% volume of zeolite and 25% biochar, 50% volume of zeolite and biochar, 25% volume of zeolite and 25% volume of zeolite, and 25% volume of biochar. The difference of volume treatment in adsorbents affected methane (CH4) and CO2 composition of biogas. Biogas purification by adsorption was conducted at 5-7 bar pressure range and room temperature. Biogas before and after purification were tested of CH4 and CO2 composition by gas chromatography. A significant reduction in CO2 was shown when 50% volume of zeolite was replaced by biochar. The highest in CO2 reduction showed by the composition of 50% sugarcane bagasse-based biochar and 50% natural zeolite. The CO2 decreases did not accompany by the CH4 increases because mesopore-sized still dominated the adsorbents’ pore size.

Experimental study of R-32/R-125 (75/25 wt.%) thermal conductivity in the vapor phase

The article presents the investigation of the thermal conductivity of binary mixture R-32/R-125 (75/25) in the gas state. Measurements were taken with a coaxial cylinders method in the temperature range of 305-426 K and the pressure range of 0.1-1.8 MPa. The dependence of thermal conductivity on pressure and temperature was discussed. The equations for thermal conductivity on the dew line and in the ideal gas state were obtained.